The first question of interest was whether preschool children with specific syndromes of ID manifested phenotypic expressions of behavioural problems, in comparison to each other as well as to children who have undifferentiated developmental delays or those who are typically-developing. Overall rates of problem behaviour in the ID groups were high, with 38.2% of these 3-year-old children scoring in the borderline or clinical range on CBCL total behaviour problems, compared to 10.3% of the typically-developing children. Behaviour problems differed by syndrome, with the highest levels found among children with autism or cerebral palsy. Children with Down syndrome were similar to typically-developing children, with these two groups generally showing the lowest levels of behaviour problems. The group with undifferentiated delays generally fell between these extremes. Similar differences were found across an array of behaviour problem measures, including the CBCL total, externalizing, internalizing, and six sub-scale scores. These findings lend support to a growing body of literature that highlights behavioural differences across syndromes and emphasizes the importance of a syndrome-specific understanding of children’s development of behavioural and psychiatric problems (e.g. Dykens, Hodapp, & Finucane, 2000
). The inclusion of a typically-developing comparison group allowed more balanced interpretation of behavioural aspects of syndrome phenotypes (Abbeduto et al. 2003
The present results are consistent with those from studies of behaviour problems in school-age children, where children with Down syndrome were more compliant, with better self-regulation, than those with autism (e.g. Bieberich & Morgan, 1998
). Also, our findings that children with Down syndrome were less emotionally reactive, with fewer internalizing or total behaviour problems than children with autism or cerebral palsy, are consistent with findings with older children and young adults showing that those with Down syndrome had fewer behavioural and psychiatric problems than persons with other ID syndromes. (e.g. Blacher & McIntyre, 2003
; Stores et al. 1998
). However, the elevated behaviour problems in our sample of young children with cerebral palsy were contrary to Blacher and McIntyre’s (2003)
finding that young adults with cerebral palsy were lower in behaviour problems than those with autism. This discrepancy may be attributable to the lower functioning level in Blacher and McIntyre’s sample of individuals with moderate or severe mental retardation, where many individuals with cerebral palsy were non-ambulatory.
Our second hypothesis concerned syndrome group differences in maternal stress and well-being. Extensive literature has established the increased risk for adjustment problems among families of children with ID (e.g. Donenberg & Baker, 1993
; Hauser-Cram et al. 2001
), and some previous work has found this negative impact on families to be associated with the level of psychiatric or behaviour problems in the child (Baker et al. 2003
). We further found that mothers’ reports of negative impact (stress) differed significantly by syndrome group at child age 3, with mothers in the autism group reporting higher negative impact than all other groups except cerebral palsy. This finding is consistent with the elevated stress reported by mothers of older children with autism (e.g. Hoppes & Harris, 1990
; Wolf et al. 1989
Interestingly, mothers of children in the cerebral palsy group did not report significantly more negative impact at age three than mothers of other groups, even though their children showed elevated levels of behaviour problems comparable to those of the autism group. These findings suggest that there are other aspects of the autism and cerebral palsy phenotypes, beyond behaviour problems, that differentially impact mothers’ experiences of stress.
We found that maternal depression did not differ significantly by syndrome group, although the rank order of syndrome groups was generally consistent with negative impact. This is consistent with previous studies in which measures that were not directly related to child-rearing did not suggest lower well-being for parents raising young children with disabilities (Baker et al., in press
; Donenberg & Baker, 1993
; Dyson, 1997
). Thus, raising a child with disabilities may at first only affect child-related domains of well-being but may, as the child grows older, affect mood and other domains as well.
We also found that mothers’ reports of the positive impact of the child did not differ by syndrome group. Positive impact may be related more to parental personality and cultural perspectives than to actual child behaviour (Baker & Blacher, 2004
). These results support the current assertion that researchers should examine positive as well as negative outcomes (Taunt & Hastings, 2002
; Stainton & Besser, 1998
), given that the specific syndrome pattern of positive impact did not mirror the pattern of negative impact.
We also examined the continuity of syndrome group differences in behaviour problems and maternal well-being over time. As expected, specific syndromes continue to relate significantly to children’s expression of behaviour problems across the preschool years. There was, however, an interaction between child age and syndrome, accounted for by the increase over time in behaviour problems among the Down syndrome group relative to other groups. Also, the relation between syndrome groups and maternal experience of stress was maintained across the preschool years. Here, too, there was an interaction between child age and syndrome, accounted for by an increase over time in negative impact among the Down syndrome and cerebral palsy groups relative to other groups. These increases in behaviour problems and negative impact among children with Down syndrome may, in part, reflect their characteristic stubbornness (Dykens et al. 2000
These findings demonstrate much continuity in relative levels of behaviour problems and negative impact across syndrome groups. However, they also suggest that the protective effects of Down syndrome against behaviour problems and maternal stress in comparison with other syndromes may be most evident among very young children and may already be diminishing by age 5. This observed trend among preschool children with Down syndrome may complement the cross-sectional results of Dykens et al. (2002)
, who found that children aged 4 to 6 years with Down syndrome showed fewer externalizing and internalizing problems than those aged 10 to 13 years. A better understanding of developmental trajectories of behavioural and psychiatric risks related to Down syndrome or other syndromes will most likely come from longitudinal studies.
Behaviour problems in children with cerebral palsy also increased from age 3 to 5, at which point they surpassed the autism group’s behaviour problems, which had decreased from age 3 to 5. This discrepancy may reflect the differences in services available to the two groups. Whereas intensive, behavioural interventions are available to many young children with autism in the early school years, services targeting children with cerebral palsy may be more likely to focus on physical, speech, or occupational therapy. These may be less likely to address behaviour problems of children with cerebral palsy with the intensity found in many autism treatment programs.
Lastly, we examined the relative contributions of syndrome, cognitive level, and behaviour problems to maternal stress. Regression analyses revealed that while child behaviour problems accounted for considerable variance in maternal stress, child syndrome contributed to maternal stress after controlling for behaviour problems and cognitive level. This remaining contribution of syndrome group was primarily accounted for by the autism group, which contributed significantly to maternal stress at ages 3, 4, and 5. One possible explanation is that there are other behaviours characteristic of autism that are not included in the CBCL listing of behaviour problems (e.g. self-injury, insistence on routine, social avoidance, dysregulated sleep and waking cycles) which appear to cause distress for caretakers. For instance, Hoppes and Harris (1990)
found that the lower interpersonal responsiveness of children with autism may be an added source of distress for their mothers. Characteristics beyond cognitive level and behaviour problems appear to affect parents raising children with other syndromes as well. Researchers have hypothesized that the physical limitations of children with cerebral palsy may be a unique source of stress for parents of these children (Pisula, 1998
), and the characteristically sociable nature of children with Down syndrome may protect against stress in parents (Hodapp et al. 2001
The current study has several limitations in the sample and method that should be considered in interpreting results. First, as the original sample was not specifically recruited to include children with specific syndromes of ID, our syndrome group sizes are small, limiting statistical power to detect group differences in behaviour problems and maternal stress. Second, parents in our sample had somewhat above average education; 48% of mothers had a college degree compared to 27.2% of adults in the general population (U.S. Census Bureau, 2004
). Third, diagnoses of syndromes were based on parent report of diagnoses from agencies serving children with ID as well as, in some cases, independent assessments; they were not otherwise verified for the purposes of this study. In particular, the autism diagnoses may be less valid than if they were based on a standardized assessment. Finally, the present analyses did not include fathers, so we do not know if the syndrome specific effects we have found hold for both parents.
We chose not to control for children’s mental age in this study. A strength of our design is that it provides a typically-developing baseline group against which to compare the syndrome groups. Removing the variance associated with mental age in our sample would, effectively, eliminate any differences between typically-developing children and children with ID on our variables of interest.
In another potential drawback of the study, mothers in our sample reported on both behaviour problems and maternal stress; therefore, the shared method variance between these measures may partially account for the relationship found between behaviour problems and maternal stress in the regression analysis. In order to assess this possibility, we repeated the regression analysis replacing mother-reported CBCL total T scores with father-reported CBCL total T scores as our measure of behaviour problems, and continuing to use mother-reported FIQ scores of negative impact. In our original analysis we established that child behaviour problems and cognitive ability contributed significantly to variance in negative impact in Step 2 of the regression, and that there was still remaining variance accounted for by syndrome group in Step 3. Using father-reported CBCL scores we found similar results. In Step 2, child behaviour problems and cognitive level accounted for 31.0% of the variance, and father-reported behaviour problems alone contributed significantly to mothers’ negative impact (t = 7.44, p < .001). Step 3, child syndrome group, also continued to contribute significantly to mothers’ negative impact, accounting for an additional 5.8% of the variance. These findings are consistent with the findings in the original regression analysis. Thus, the relationship between child behaviour problems and maternal stress persists even after removing the shared method variance.
In sum, syndrome specific behavioural patterns were manifested in children at 3 years of age and were relatively stable across the preschool years. Syndrome made a significant contribution to maternal stress above and beyond the contribution of cognitive ability and behaviour problems. This finding underscores the need for the identification and examination of additional factors beyond behavioural problems that may differ by syndrome. For instance, personality characteristics, availability of intervention services, occupational or physical limitations, and other developmental features of specific syndromes should be explored for their impact on parent well-being. This research also highlights the importance of understanding syndrome-specific age-related patterns of behaviour problems, as evidenced by the increase in such problems among children with Down syndrome over time. Finally, these findings suggest that interventions that are targeted to specific syndromes of ID, and their associated phenotypic expressions of behavioural and psychiatric problems, may be particularly effective, not only for children but also for the adjustment of their mothers and other family members.